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Holmes, J.A.

Paper Title Page
MOPC003 Benchmarking of Simulation Codes Based on the Montague Resonance in the CERN Proton Synchrotron 330
 
  • I. Hofmann, G. Franchetti
    GSI, Darmstadt
  • J.F. Amundson, P. Spentzouris
    Fermilab, Batavia, Illinois
  • S.M. Cousineau, J.A. Holmes
    ORNL, Oak Ridge, Tennessee
  • M. Giovannozzi, E. Métral
    CERN, Geneva
  • F.W. Jones
    TRIUMF, Vancouver
  • A.U. Luccio
    BNL, Upton, Long Island, New York
  • S. Machida
    KEK, Ibaraki
  • J. Qiang, R.D. Ryne
    LBNL, Berkeley, California
 
  Experimental data on emittance exchange by the space charge driven ‘‘Montague resonance'' have been obtained at the CERN Proton Synchrotron in 2002-04 as a function of the working point. These data are used to advance the benchmarking of major simulation codes (ACCSIM, IMPACT, MICROMAP, ORBIT, SIMBAD, SIMPSONS, SYNERGIA) currently employed world-wide in the design or performance improvement of high intensity circular accelerators. In this paper we summarize the experimental findings and compare them with the first three steps of simulation results of the still progressing work.  
TPAT031 Painting Self-Consistent Beam Distributions in Rings 2194
 
  • J.A. Holmes, S.M. Cousineau, V.V. Danilov
    ORNL, Oak Ridge, Tennessee
 
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge.

We define self-consistent beam distributions to have the following properties: 1) time-independence or periodicity, 2) linear space charge forces, and 3) maintainance of their defining shape and density under all linear transformations. The periodic condition guarantees zero space-charge-induced halo growth and beam loss during injection. Some self-consistent distributions can be manipulated into flat, or even point-like, beams, which makes them interesting to colliders and to heavy-ion fusion. This paper presents methods for painting 2D and 3D self-consistent distributions and for their manipulation to produce flat and point-like beams.

 
TPAT032 Transverse Stability Studies of the SNS Ring 2254
 
  • J.A. Holmes, V.V. Danilov
    ORNL, Oak Ridge, Tennessee
  • L.K. Jain
    UW/Physics, Waterloo, Ontario
 
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge.

Detailed studies of the transverse stability of the SNS ring have been carried out for realistic injection scenarios. For coasting beam models and single harmonic impedances, analytic and computational results including phase slip, chromaticity, and space charge are in excellent agreement. For the dominant extraction kicker impedance and bunched beams resulting from injection, computationally determined stability thresholds are significantly higher than for coasting beams. At this time, we have no analytic model to treat the bunched beam case, but we present a formulation that provides an approach to this problem.

 
WOAC009 Techniques for Measurement and Correction of the SNS Accumulator Ring Optics 674
 
  • S. Henderson, P. Chu, S.M. Cousineau, V.V. Danilov, J.A. Holmes, T.A. Pelaia, M.A. Plum
    ORNL, Oak Ridge, Tennessee
 
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos and Oak Ridge.

The Spallation Neutron Source (SNS) Accumulator Ring will reach peak intensities of 1.5x1014 protons/pulse through multi-turn charge-exchange injection. Accumulation of these unprecedented beam intensities must be accomplished while maintaining extremely low losses (less than 1 W/m). It is anticipated that the control of the ring optics will be important for achieving these low loss rates. We describe our plans for measuring and correcting the optical functions of the accumulator ring lattice.

 
ROPB010 Self-Consistent Electron-Cloud Simulation for Long Proton Bunches 722
 
  • A.P. Shishlo, S.M. Cousineau, V.V. Danilov, S. Henderson, J.A. Holmes, Y. Sato
    ORNL, Oak Ridge, Tennessee
  • S.-Y. Lee
    IUCF, Bloomington, Indiana
  • R.J. Macek
    LANL, Los Alamos, New Mexico
 
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge.

The results of numerical electron-cloud simulations for long-bunch proton beams in accumulator rings are presented and compared with data from the Proton Storage Ring at LANL. The frequency spectra and growth rate of proton-bunch transverse instabilities are studied as functions of the RF cavity voltage, external magnetic fields, beam pipe surface properties, and other factors. We used the recently developed electron-cloud module in the ORBIT code. The model includes a fully self-consistent coupled treatment of the "proton bunch – electron-cloud" dynamics and the multipacting process with a realistic secondary emission surface model. Realistic lattices and proton bunch distributions are used. The efficiency of electron-cloud instability suppression has also been studied using a new ORBIT model.

 
FPAE024 Studies Performed in Preparation for the Spallation Neutron Source Accumulator Ring Commissioning 1859
 
  • S.M. Cousineau, V.V. Danilov, S. Henderson, J.A. Holmes, M.A. Plum
    ORNL, Oak Ridge, Tennessee
 
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge.

The Spallation Neutron Source accumulator ring will compress 1.5?1014, 1 GeV protons from a 1 ms bunch train to a single 695 ns proton bunch for use in neutron spallation. Due to the high beam power, unprecedented control of beam loss will be required in order to control radiation and allow for hands-on maintenance in most areas of the ring. A number of detailed investigations have been performed to understand the primary sources of beam loss and to predict and mitigate problems associated with radiation hot spots in the ring. The ORBIT particle tracking code is used to perform realistic simulations of the beam accumulation in the ring, including detailed modeling of the injection system, transport through the measured magnet fields including higher order multipoles, and beam loss and collimation. In this paper we present the results of a number of studies performed in preparation for the 2006 commissioning of the accumulator ring.